Universal pigment pastes and their use for the manufacture of aqueous paints

Abstract

A pigment paste for use in preparing aqueous paints includes a binder that includes at least one polyurethane acrylate resin, water as a solvent, and a pigment component that may be an organic pigment, an inorganic pigment, or carbon black. Preferably, the polyurethane acrylate is a product of a process comprising polymerizing one or more ethylenically unsaturated monomers in the presence of a polyurethane resin, which has a number-average molecular weight from about 200 to about 30,000, and which contains, on average, from about 0.05 to about 1.1 polymerizable double bonds per molecule. The reaction product is then converted into an aqueous dispersion, and mixed with the pigment and water to form the pigment paste. A preferred pigment paste contains from 10 to 35% of the polyurethane acrylate resin, from 10 to 65% water, and a percentage of the pigment component which varies, depending on the material selected.

What is claimed is:  
     
         1 . A pigment paste comprising: 
 a) a binder, comprising at least one polyurethane acrylate which is a product of a process comprising the steps of: 
 polymerizing, in an organic solvent or in a mixture of organic solvents, 
 ethylenically unsaturated monomers, or a mixture of ethylenically unsaturated monomers, in the presence of  
 a polyurethane resin which has a number-average molecular weight of from 200 to 30,000, and which contains on average from 0.05 to 1.1 polymerizable double bonds per molecule, and  
 
 converting the resulting reaction product into an aqueous dispersion;  
 said binder being present in the form of from 10 to 35% by weight of at least one polyurethane acrylate resin, based on the solids content;  
   b) from 10 to 65% by weight of water; and    c) at least one pigment component, selected from the group consisting of: 
 i) an organic pigment, comprising 
 A. from 18 to 40% by weight of at least one organic, transparent pigment, or  
 B. from 30 to 50% by weight of at least one organic, opaque pigment,  
 
 ii) from 30 to 80% by weight of at least one inorganic pigment excluding white pigments, or from 50 to 70% by weight of white pigment,  
 iii) from 8 to 15% by weight of carbon black,  
 iv) and mixtures thereof; the proportions by weight of the pigment component being based on the overall weight of the pigment paste, and wherein the pigment/binder ratio is between 5:1 and 2:1.  
   
     
     
         2 . Pigment paste according to  claim 1 , comprising 
 a) from 15 to 25% by weight of at least one polyurethane acrylate resin, based on the solids content,    b) from 20 to 50% by weight of water and    c) wherein the pigment component is selected from the group consisting of: 
 from 24 to 35% by weight of at least one organic, transparent pigment, from 33 to 45% by weight of at least one organic, opaque pigment,  
 from 38 to 50% by weight of at least one inorganic pigment excluding white pigments,  
 from 9 to 12% by weight of carbon black, and mixtures thereof;  
 the proportions by weight of the pigment component being based on the overall weight of the pigment paste.  
   
     
     
         3 . Pigment paste according to  claim 1  further comprising one or more supplemental constituents selected from the group consisting of: 
 d) at least one dispersing auxiliary;  
 e) one or more organic solvents;  
 f) one or more binders other than polyurethane;  
 g) one or more fillers or extenders; and  
 h) one or more customary auxiliaries and/or additives;  
 and mixtures thereof, the proportions by weight of each of the supplemental constituents d) to h) being based on the overall weight of the respective pigment paste.  
 
     
     
         4 . Pigment paste according to  claim 1 , having a solids content of from 25 to 85% by weight, a pH of from 7 to 9, and a viscosity, at a temperature of 23° C. and a shear rate of 1000 s −1 , of from 50 to 800 mPa.s.  
     
     
         5 . Pigment paste according to  claim 1 , wherein the pigment/binder ratio in the pigment paste is between 5:1 and greater than 3:1.  
     
     
         6 . An aqueous paint comprising one or more pigment pastes according to  claim 1 .  
     
     
         7 . Aqueous paint according to  claim 6 , comprising from 10 to 60% by weight of the at least one pigment paste.  
     
     
         8 . Aqueous paint according to  claim 6 , wherein the binder comprises at least one polyurethane acrylate.  
     
     
         9 . Method of coating substrates, comprising the step of applying an aqueous paint according to  claim 6  to a substrate.  
     
     
         10 . Method according to  claim 9 , wherein the aqueous paint is a solid color basecoat.  
     
     
         11 . Mixer system for the preparation of aqueous coating compositions, characterized in that the mixer system comprises at least two pigment pastes according to  claim 1 .  
     
     
         12 . The pigment paste of  claim 1 , wherein the polyurethane resin which has a number-average molecular weight of from 0.3 to 0.7 polymerizable double bonds per molecule.  
     
     
         13 . An aqueous paint according to  claim 6 , said aqueous paint being curable by exposure to radiation.  
     
     
         14 . An aqueous paint according to  claim 6 , said aqueous paint comprising an automotive coating composition.  
     
     
         15 . A pigment paste comprising: 
 a) a binder, comprising from 10 to 35% by weight of at least one polyurethane acrylate resin, based on the weight of the total solids content of the paste, said polyurethane acrylate resin being a product of a process comprising the steps of: 
 polymerizing, in an organic solvent or in a mixture of organic solvents, 
 ethylenically unsaturated monomers, or a mixture of ethylenically unsaturated monomers, in the presence of a polyurethane resin which has a number-average molecular weight of from 1000 to 5000, and which contains on average from 0.2 to 0.9 polymerizable double bonds per molecule; and  
 
 converting the resulting reaction product into an aqueous dispersion;  
   b) from 10 to 65% by weight of water; and    c) at least one pigment component, selected from the group consisting of: 
 from 18 to 40% by weight of at least one organic, transparent pigment;  
 from 30 to 50% by weight of at least one organic, opaque pigment;  
 from 30 to 80% by weight of at least one inorganic pigment excluding white pigments;  
 from more than 50 to 70% by weight of white pigment, and  
 from 8 to 15% by weight of carbon black;  
 the proportions by weight of the pigment component being based on the overall weight of the pigment paste;  
   said pigment paste having a solids content of from 25 to 85% by weight, a pH of from 7 to 9, and a viscosity, at a temperature of 23° C. and a shear rate of 1000 s −1 , of from 50 to 800 mPa.s., and wherein the pigment/binder ratio is between 5:1 and 2:1.    
     
     
         16 . Pigment paste according to  claim 15 , wherein the pigment/binder ratio in the pigment paste is between 5:1 and greater than 3:1.